知识与财富的链接
滇中玉溪-昆阳一带广泛出露的中元古界昆阳群是一套与晋宁运动密切相关的浅变质火山-沉积岩系,其形成时代、沉积充填序列及大地构造属性一直存在争议。出露于峨山县美党地区的昆阳群黑山头组富良棚段发育有厚近百米的安山质熔结凝灰岩、晶屑凝灰岩、玄武岩及岩屑凝灰岩。对样品D0121-1及D0121-2进行同位素年代学研究,分别获得LA-ICP-MS锆石U-Pb年龄加权平均值为1007±13Ma和1005±18Ma;同时,样品D0121-2中还获较多的2200±15Ma继承性锆石,推测滇中地区应存在古元古代的地质体。2件样品锆石的Th/U值均大于0.3,均具清晰的振荡环带结构,均为岩浆成因的锆石,表明黑山头组富良棚段形成于中元古代晚期,属于与造山作用相关的火山岩系,可能是罗迪尼亚超大陆事件在扬子陆块的响应,是全球格林维尔期造山过程的组成部分。
Mesoproterozoic Kunyang Group,which is widely exposed in Yuxi-Kunyang area in central Yunnan Province, consists of metamorphic volcanic sedimentary rocks that are closely related to the Jinning movement. The chronology, sedimentary filling series and geotectonic features of Kunyang Group are problems of long controversy. There are andesitic ignimbrite, crystal tuff, basalt and lithic tuff several hundred meters in thickness in Fuliangpeng member of Heishantou Formation within Kunyang Group exposed in Meidang area, Eshan County. Two samples of D0121-1 and D0121-2 were used for isotopic dating. The weighted average ages of U-Pb zircon LA-ICP-MS obtained from sample D0121-1 and D0121-2 are 1007±13Ma and 1005±18Ma respectively.
In addition, ancient inherited zircon 2200±15Ma was found in sample D0121-2. It is inferred that there is a Paleproterozoic geological body in central Yunnan Province. The Th/U ratios of zircon obtained from both samples are higher than 0.3, suggesting magmatic zircon. It is considered that Fuliangpeng member of Heishantou Formation was formed in the Late Mesoproterozoic period and belonged to the volcanic rock series related to orogeny, which was probably the response of the Rodinia Supercontinent Events in Yangtze continental block, being a part of the global Greenville orogenic process.
